Resin tubes have been prevalently applied to fuel lines of automobiles in recent years.
Resin tubes have many advantages; resin tubes are not rusted whereas metal tubes are rusted, are easily workable, provide a high degree of freedom of design and are lightweight.
It is a problem, when resin tubes are applied to fuel lines, that gasoline permeates resin tubes and dissipates. Regulations for regulating the permeation of fuel through resin tubes have become progressively severe.
It is an urgent problem to provide resin tubes intended for application to fuel lines additionally with a property that makes it difficult for fuel to permeate resin tubes. Such a property will be referred to as a “low-permeable property”.
A resin tube for fuel lines is regarded as having a low-permeable property when the amount of hydrocarbons permeated the resin tube measured by a CARB DEL method using a SHED tester is 50 mg/m·day or below.
A known laminated resin tube has an innermost tube, which comes into contact with gasoline, made of a resin having a low-permeable property, and an outermost tube made of a polyamide resin and bonded to the innermost tube by an adhesive layer to improve low-permeable property.
The applicant of the present invention patent application proposed a laminated resin tube having an improved low-permeable property in Patent document 1. This previously proposed laminated resin tube has at least two low-permeable resin tubes, and one of the low-permeable resin tubes is made of one of thermoplastic resins including ethylene tetrafluoroethylene resins (ETFE resins), liquid-crystalline polymers (LCPs), polyphenylene sulfide resins (PPS resins), ethylene-vinyl alcohol resins (EVOH resins), and polybutylene naphthalate resins (PBN resins).
The fluorocarbon resins, namely, the ETFE resins, among those resins are very excellent in the low-permeable property. A known laminated resin tube has an outer tube made of polyamide 12 and an inner tube made of a fluorocarbon resin.
Patent document 1: Jpn. Pat. App. No. 2002-338173 (JP 2004-169851 A)